The invention disclosed herein relates to apparatus for withdrawing liquid samples from vessels and transferring the withdrawn liquid, particularly liquids such as body fluids or liquids which should not come into contact with personnel handling same during, for example, testing and analysis of the liquids.
Currently blood and other body fluids are routinely taken from patients for testing The sophistication of modern testing apparatus which typically include a computer enables a multitude of tests to be conducted on such body fluids Because such body fluids may contain bacteria, viruses, etc., they are typically contained in closed vessels and containers such as vials, collection tubes and the like. Frequently, during testing it is necessary for laboratory personnel to manually withdraw a small portion of such a liquid sample from a vessel. To prevent leakage or spillage of liquid from the vessel and possible contamination of laboratory personnel with the liquid, and to maintain the integrity of the liquid sample remaining in the vessel for possible further testing, it is desirable that the vessel not be opened to withdraw a portion of the liquid sample therefrom.
In addition, it is desirable that the liquid sample in the vessel be disturbed as little as possible during withdrawal of the small portion from the vessel to prevent mixing of separated components or liquid phases of the liquid sample and/or to prevent possible damage to the remaining liquid sample. This allows further testing of the remaining liquid sample, and where it is desirable to withdraw liquid from given layers of the sample, further testing may proceed without waiting for the liquid sample to settle.
An important consideration in the design, construction and use of apparatus for withdrawing such liquids is the prevention of contamination of personnel handling the apparatus and the liquid sample vessels. Thus, not only is it important that there be no leaking or escaping of sample from the apparatus and/or sample vessel during normal use of the apparatus, but the apparatus must be relatively safe to handle so it is not easy for a person handling the apparatus to be pricked by a cannula or sharp part of the apparatus.
A pump device for aspirating a liquid sample from a collection tube is described in the November, 1989 issue of "Clinical Lab Products", Vol. 18, No. 11, page 1. The pump device described in the "Clinical Lab Products" publication, according to a device inspected by the applicants, comprises two cannulas that pass through the collection tube stopper. One cannula is communicated with a bellows which when compressed introduces pumping air into the collection tube. A sample withdrawal tube is passed through the other cannula, and liquid sample is removed from the collection tube through this sample withdrawal tube. Air to recharge the bellows when compression thereof is released is sucked into the collection tube through the sample withdrawal tube, and therefore such recharging air passes through the remaining liquid sample in the collection tube and disturbs the remaining liquid in the collection tube, particularly when the bellows is operated sharply. This may be disadvantageous in certain applications such as where the liquid may settle into layers or phases and it is desired to withdraw liquid from a particular layer, or when the liquid is fragile. For example, when the liquid sample is blood, and it is desired to withdraw blood serum, air passing through the blood produces bubbles in the blood which causes the blood serum to mix with the red cells.
An additional disadvantage of the pump device inspected by the applicants is the lack of a seal between the sample withdrawal tube and the cannula which may allow contaminated liquid sample to leak or escape during normal use of the device, particularly under the action of the pumping air during pumping.
As discussed above, the person handling the liquid withdrawal apparatus should be protected against being pricked and/or against coming into contact with the liquid sample. The device described in the "Clinical Lab Products" publication, according to the device inspected by the applicants, is somewhat difficult to connect to the sample collection tube because the apparatus is difficult to grasp while applying the considerable force necessary to push the two cannulas through the stopper. As a result, the cannula tips may accidently be pushed off the stopper and prick a finger of the person connecting the device to the collator tube. Also, because that device may leak during normal use as described above, there is also a risk that the person handling the device may be contaminated by liquid sample.